Switzerland

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Many natural phenomena on Earth also occur on other planets in the solar system under the right conditions. Scientists have recently found evidence indicating the presence of something close to a rainbow on a strange exoplanet. 

"Glory" is a phenomenon which occurs when light hits clouds made up of homogeneous substances in the form of spherical droplets. This phenomenon is a possible explanation for a mystery regarding observations of exoplanet WASP-76B. 

WASP-76B is a scorching gas giant where molten iron rains. Researchers from ESA and the University of Bern in Switzerland have observed more light on its eastern terminator than its western terminator with the CHEOPS space telescope. 

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CHEOPS has made 23 observations of WASP-76B in visible and infrared light, including phase curves, transits, and secondary eclipses.

Phase curves are continuous observations that track a planet's complete revolution. When a host star eclipses its planet, a secondary eclipse occurs. Later, researchers compare the light seen during such an eclipse with the total light. Usually, they use secondary eclipses to observe planets like WASP-76B.

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Observations of the phase curve of WASP-76B can continue even when the planet is eclipsing its star. During such observations, CHEOPS detected excess light on the planet's night side before the eclipse.

Since WASP-76B is a super hot exoplanet, clouds do not obscure the atmosphere during the day, making it easier to detect atmospheric detections.

According to a previous study, researchers observed an asymmetry in iron content between the day-side and night-side terminators, making the planet unique. Moreover, there was not much gaseous iron in the upper atmosphere of the day-side limb compared to the night-side limb. 

Hubble observations suggest thermal inversion on the night side of a planet causes iron to rain down on the day side and form liquid iron clouds. These clouds are crucial as light from the star can create the effect of glory when it reflects off them.

The research paper published in Astronomy & Astrophysics, "Explaining the observation with the glory effect would require spherical droplets of highly reflective, spherically shaped aerosols and clouds on the planet's eastern hemisphere."

Glories have been seen off on Earth and in clouds of Venus. Similar to WASP-76B, researchers have observed more pre-eclipse light on Venus. Thus, future observations with more powerful telescopes can help determine how similar the phenomenon on WASP-76 is to that on Venus.

These phenomena could reveal more about the atmospheric composition of exoplanets, including the presence of water and habitability. While the glory of WASP-76b is not yet proven, it is far from a simple rainbow.

(With inputs from agencies)